Multiple casting apparatus and method

ABSTRACT

An apparatus and method for pressure casting a battery part wherein an extendible piston includes sidewalls for shutting off the supply of molten lead and an impact surface that extends in a side-to-side condition to form an end surface of a battery part cavity so that when the extendible piston is brought into an intensifying condition the extendible piston shuts off further supply of molten metal while a heat source maintains the lead in a molten state as the impact surface of the piston forms a side-to-side mold cavity surface to complete the mold cavity surface thereby eliminating unevenness in the surface of the finished battery part by generating a force with the extendible piston which is sufficient to form a battery part so that upon removal from the mold the batter part is substantially free of tears and cracks as well as surface irregularities.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] None

REFERENCE TO A MICROFICHE APPENDIX

[0003] None

FIELD OF THE INVENTION

[0004] This invention relates generally to pressure casting and, morespecifically to die casting of lead or lead alloy battery parts such asbattery terminals to form a finished battery part while at the same timeinhibiting the formation of cracks and tears during and after thesolidification of the battery part through peripherally contracting themold cavity volume by bringing an entire mold face toward a mold cavityto reduce the bounded surface volume of the mold cavity withoutdisrupting the integrity of the faces of the mold part solidifyingwithin the bounded surface volume.

BACKGROUND OF THE INVENTION

[0005] Battery parts such as battery terminals, which are typically madeof lead or a lead alloy, are usually cold formed in order to produce abattery terminal that is free of voids and cracks. If lead or lead alloybattery parts are pressure cast, air is left in the battery part cavityin the mold so that as the lead solidifies, the air bubbles prevent thebattery part from cracking. That is, the air bubbles act as fillers sothe lead remains distributed in a relatively uniform manner throughoutthe battery part. Unfortunately, air bubbles within the battery partscause the battery parts to be rejects as the air bubbles can producelarge voids in the battery part. In order to minimize the air bubbles inthe battery part, a vacuum can be drawn in the battery part cavity mold;however, although the vacuum removes air from the mold and inhibits theforming of air bubbles in the battery part, the battery parts cast witha vacuum in the battery part cavity oftentimes solidify in an unevenmanner producing battery parts with cracks or tears which make thebattery parts unacceptable for use.

[0006] The process of pressure casting or die casting of battery partswherein intensification of the battery part is used to form batteryparts substantially free of cracks and tears is more fully described inmy copending applications Ser. No. 09/170,247, filed Oct. 13, 1998,titled Apparatus for and Method of Casting Battery parts; Ser. No.09/458,198 filed Dec. 10, 1999 title Multiple Casting Apparatus andMethod and Ser. No. /09/321,776 filed May 27, 1999 titled Apparatus andMethod of Forming Battery Parts which are herein incorporated byreference.

[0007] In one such embodiment, a battery part is cast which issubstantially free of cracks and tears by pressure casting a lead alloywhile a vacuum is being applied to the battery part cavity. At themoment when the lead in the battery part cavity reaches theliquid-to-solid transformation stage, the part is intensified by drivinga piston into the mold cavity to rapidly reduce the volume of the moldfor solidification. By precisely controlling the time of application ofan external compression force to the molten lead in the battery partcavity, and consequently, the time at which the volume of the batterypart cavity is reduced, one can force the molten lead or lead alloy inthe flowable state into a smaller volume where the pressure on thebattery part cavity is maintained. By maintaining the pressure on thebattery part cavity during the solidification process by intensification(driving a piston into the lead), the battery part can be cast in a formthat is substantially free of cracks and tears.

[0008] In another embodiment, the mold for forming the pressure castbattery part is sealed off while the molten lead is still in the moltenstate and before the molten lead can begin to solidify the supply ofpressurized lead is shut off and at the same time the internal pressureof the molten lead is increased by driving a piston into the moltenmetal. This intensification process is suited for those applicationswhere the entire mold can withstand the higher pressures. That is, whenthe liquid metal is in a molten state an increase in pressure of themolten lead throughout the mold and the maintaining of the increasedpressure during solidification can produce a battery part free of tearsand cracks. This process of intensification by driving a piston into themold allows one to obtain greater molding pressure than is availablewith conventional pressure casting techniques.

[0009] In another embodiment, the cast battery part is subjected to atleast a partial cold forming during the volume contraction step byrapidly driving a piston into the solidified cast battery part withsufficient force to cold form a portion of the lead in the battery partto thereby produce a battery part that is free of cracks and tears. Thismethod of partial cold form intensification is more suitable for thosebattery parts where one does not want to subject the mold to excessivelyhigher pressures than the die casting pressures.

[0010] In the present invention a finished battery is die cast which issubstantially free of cracks and tears is formed by extending a pistonthat first shutoffs the flow of molten lead into and out of the moldcavity. Further extension of the piston brings a piston face that formsa bounded end face of the mold part toward the other faces of the mold.Instead of driving a piston into the mold cavity to increase thepressure of the die cast battery part the entire mold face is broughttoward the set of other mold faces to decrease the volume of the mold.Thus the shutoff and intensification are accomplished by a single strokeof an extendible piston carrying a mold face thereon.

[0011] By finished surface it is meant that the surface of the batterydoes not contain flashing or irregularities where the molten lead wassupplied through a gate. That is, in die casting the runner thatsupplies lead to the mold is usually broken off when the battery part isremoved from the mold thus leaving an unfinished surface. Sinceirregularities can create problems in electrical operation of thebattery part it is desired to have a smooth finished surface over theentire battery part. As pointed out, such finished surfaces are usuallyobtained only with cold forming a battery part. The present inventionprovides such a finished surface without having to cold form the batterypart. In addition, one can also increase the pressure sufficiently toinhibit voids and cracks in the battery part.

[0012] In the present invention a retractable piston has an impactsurface or mold face that forms an entire side-to-side mold face or moldsurface of the battery part thereby eliminating the formation of a localirregularity in the portion of the surface of the battery part thatwould occur if the piston penetrated a portion a mold face i.e. breakingthe surface plane of the mold cavity. The use of a side-to-side orbounded mold face that does not break the surface plane of the moldcavity substantially eliminates the need to finish the battery part.That is, once the part is removed from the mold it is ready for usesince the surface plane of the mold cavity has not been broken orpenetrated by the moving end face. In addition, since the entireside-to-side surface of the battery part is impacted the precisiontiming of the intensification step is eliminated. That is, since theintensification pressure is applied on a side-to-side portion of thebattery part cavity the lead can be in either the liquid, solid or mushstate since the all the lead can be confined and squeezed within thecavity of the battery part mold cavity.

SUMMARY OF THE INVENTION

[0013] An apparatus for pressure casting a battery part wherein a moldincludes a set of faces to form a portion of a battery part mold cavityand an extendible piston having a battery part mold cavity face thatextends in a side-to-side condition on the piston with the facescoacting to form a bounded battery part mold cavity. The piston includessidewalls for shutting off the supply of molten lead to and from themold cavity so that when the extendible piston is brought toward thebattery part mold cavity the extendible piston first shuts off a furthersupply of molten metal to the battery part mold cavity as well as egressof metal from the battery part mold cavity to create a closed batterypart mold cavity. The battery part mold cavity peripherally contracts asthe face of the piston forms an entire bounded face of the battery partmold cavity. The peripherally contraction eliminates localized surfacepenetration of the face of a battery part as the peripheral surface ofthe cavity remains intact as it is decreased. The result is the batterypart in the battery part mold cavity have non-disturbed faces when thebattery part mold cavity is brought to a closed condition. Ifintensification is desired one maintains the pressure on the lead as itsolidifies so that upon solidification the part is substantially free oftears and cracks as well as surface irregularities.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a partial sectional view of the apparatus of the moldand extendible pistons for forming a battery part in an open condition;

[0015]FIG. 2 is partial sectional view of the apparatus of FIG. 1showing one of the extendible pistons extended to form part of aninterior surface for a battery part and the other extendible piston in aretracted condition to allow molten lead to flow into the mold;

[0016]FIG. 3 is the partial sectional view of the apparatus of FIG. 1showing the extendible piston in an engaged condition that preventsfurther molten lead to from flowing into the battery part cavity and atthe same time intensifying the lead in the battery part cavity;

[0017]FIG. 4 shows an isolated view of the multiple mold surfaces thatcoact to form a battery part mold cavity wherein moving an end face ofthe mold cavity contracts the volume of the cavity;

[0018]FIG. 5 shows an isolated view of the mold faces with the moldcavity in an open condition to allow flow of molten lead therein;

[0019]FIG. 6 is an isolated view of the mold faces of FIG. 5 with theend face in a sealing condition or closed mold condition; and

[0020]FIG. 7 is an isolated view of the mold faces of FIG. 5 with themold cavity in a contracted condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021]FIG. 1 is a partial sectional view of apparatus 10 for faceintensification during die casting of battery parts. Apparatus 10includes an upper first mold part 11 and a lower second mold part 12that are held proximate each other by a member (not shown) to form acavity 16 therein. The two parts are joined a parting surface 12 p thatextends between the two mold parts.

[0022] Located partially in mold part 11 is a first extendiblecylindrical piston 14 which is axially slideable into mold part 11.Piston 14 includes a cylindrical surface 14 a for slideingly engagingcylindrical surface 11 a in mold part 11 to prevent molten lead fromflowing therepast. The end of piston 14 includes a hemispherical recess14 c and an annular impact surface 12 e there around with the annularimpact surface 12 e located in a single plane. Extendible piston 14slidingly engages the sidewall 11 a of mold part 11 to allow for axialinsertion thereof to bring the impact surface 12 e downward to become aportion of the battery part cavity surfaces formed by the sidewalls ofcavity 16. That is, the impact surface 12 e forms an entire end orside-to-side top surface to the battery part cavity 16 therebypreventing formation of local irregularities in the end surface of abattery part cast since the entire end face 12 e can be brought inwardto form the battery part mold cavity.

[0023] Extending downward into mold part 11 is a first runner or gate 17terminating in a mouth 17 a and a second runner 18 or vent terminatingin a mouth 18 a. Runner 17 is connected to a supply of molten lead (notshown) and vent 18 connects to a vent valve 18 to allow air to escapefrom the mold cavity. Located around the mold part 11 is a heater 20 formaintaining the temperature of the upper portion of mold part 11sufficiently hot to maintain the lead in runners 17 and 18 in a moltenstate during the intensification and casting of a battery part. Locatedbeneath mold part 12 is a cylindrical pin 13 for that extends throughcavity 16 and into a cylindrical sleeve 15 in piston 14. Pin 13 has acylindrical surface 13 that slidingly engages cylindrical sleeve 15 tomaintain a sliding relationship between piston 14 and pin 13.

[0024]FIG. 2 is partial sectional view of the apparatus of FIG. 1showing the pin 13 extended upward into battery part cavity 16 to formpart of an interior surface for a battery part. The top extendiblepiston 14 is in a retracted condition to allow molten lead to flow intothe mold cavity 16 through the runners 17 and excess lead and air toevacuate through runner 18, as indicated by the arrows. Thus as evidentby FIG. 2 the molten lead flows around the extendible piston 13 into theannular battery part cavity 16. Note, at this point end annular surface12 e forms no part of the contiguous boundary wall of the battery partcavity 16. That is the mold cavity is in an open condition so thatmolten lead can flow into cavity 16 thought gate 17.

[0025] While the present battery part cavity is shown with an annularshaped battery part cavity one can use the present process without a pin13 to obtain a non-annular shaped battery part.

[0026]FIG. 3 is the partial sectional view of the apparatus of FIG. 1showing the extendible piston 14 in an engaged or closed condition thatprevents further molten lead from flowing into or out of the batterypart cavity 16 and at the same time in a condition that one canintensifies the lead in the battery part cavity 16 to inhibit theformation of tears and cracks. In the position shown, the sidewalls 14 aof piston 14 close off the mouths 17 a and 18 a to prevent furthermolten lead from flowing into or out of battery part cavity 16. Moltenlead 30 is shown in battery part cavity 16 as well as in runners 17 and18.

[0027] During the extension of member 14 excess molten lead in chamber31 is forced backward or backwashed into runners 17 and 18 until the endof extendible piston covers the mouths 17 a and 18 a of the runners 17and 18. This ensures that the mold cavity is filled with molten lead. Atthis point battery part cavity 16 becomes closed as no lead can leavethe battery part cavity. Further downward pressure on extendible piston14 brings end face 12 e downward decreasing the volume of the batterypart cavity without penetration of a surface. By maintaining thepressure one intensifies the cast part by increasing the internalpressure of the lead in the battery part cavity 16 sufficiently high sothat when the lead solidifies the part is substantially free of tearsand cracks. Thus, the intensification process of the present methodcomprises creating an abrupt increase in the internal pressure of thelead in a mold cavity to a level which is sufficient to reduce the sizeof trapped air bubbles therein by bringing an entire face of the batterypart mold cavity toward the other mold faces so that when the batterypart solidifies the battery part is substantially free of cracks andtears.

[0028] In the embodiment shown the annular end 12 e of the extendiblepiston 14 is driven to an adjoining condition at the comer line of thecavity of the battery part cavity surface 16 in mold part 11. By havingthe impact surface 12 e form the entire bounded top surface of thebattery part cavity one eliminates the formation of irregularities inthe finished battery parts since the top surface of the battery partcavity remains a continuous surface.

[0029]FIG. 3 shows that the battery part cavity is formed of multiplesurfaces or faces some of which are formed by the extendible piston andothers that are formed by the mold parts. That is, the battery partcavity has an interior surface 12 d formed by piston 13. Mold part 12includes annular mold part surface 12 b and lateral mold part surface 12a. Mold part 11 includes the lateral mold part surface 12 c with impactsurface 12 e defining the final surface portion of the battery part.

[0030] As can be seen pin 13 slidingly mates with the cylindrical recess14 c in piston 14 thus ensuring that both pin 13 and piston 14 are inaxial alignment and that the interior surface of the cast part iscentrally positioned within the battery cavity 16.

[0031] With the present apparatus and method one eliminates any runnermarks as well as intensification marks on the finished battery partsince the battery part is contiguously defined by the coactions of theextendible pistons and the battery part molds. In addition, thealignment of the extendible pistons allows for an on-the-go formation ofthe battery cavity.

[0032] In the present process the method of die casting a finishedbattery part while minimize cracks and voids in the battery partincludes the steps of forming a mold 11, 12 with the mold defining aplurality of faces 12 a, 12 b, 12 c 12 f for a first portion of abattery part mold cavity 16. One forming a gate passage 17 that fluidlyconnected to the first portion of the battery part mold cavity 16 whenthe mold is in a pouring condition. One forms a moveable member orpiston 14 the moveable member includes a portion 12 e defining a furtherface of the battery part mold cavity 16 with the plurality of faces 12a, 12 b, 12 c 12 f and the further face 12 e defined a surface boundedmold cavity when the moveable member is in a closed condition asillustrated in FIG. 3. By pouring a lead containing metal in a fluidstate into the gate 17 of the mold when the mold cavity 16 is in an opencondition as illustrated in FIG. 2 allows molten lead to flow into themold cavity 16. By allowing the lead containing metal to fill the firstportion of the battery part mold cavity 16 of volume V₁ (FIG. 4); andthen driving the moveable member 14 toward the first portion the batterymold part one closes off the gate passageway 17 and the vent passage 18.One continues to drive the movable member 14 toward the first portion ofthe battery mold part cavity 16 until the further face 12 e forms thefinal surface to close the mold cavity 16. By applying pressure tomember 14 one can increase the internal pressure of the lead in the moldincreases sufficiently to force lead into any solidification voidsformed in the batter part. Next, one allows the battery part to solidifyunder pressure. Once the battery part is solidify one can removing themold from the battery part to produce a finished battery part.

[0033] The method of forming a finished battery part can be obtained bypouring a lead containing metal in a liquid state into an open batterycavity 16 defined by a first set of faces in a battery part mold andallowing the lead containing metal to solidify around the first set offaces in the battery part mold and then driving a member having aportion defining a completion face 12 e toward open battery cavity 16until the completion face 12 e and the first set of faces coact to forma closed surface for the battery cavity. By maintaining pressure on thebatter part therein during solidification of the metal in a liquid stateit forces molten lead to flow into any solidification voids formedduring solidification phase of the molten lead in the battery partcavity.

[0034]FIG. 4 illustrate the set of faces for forming the die castbattery part. For ease in comprehension the mold parts have been leftout with exception of the faces that form the mold cavity. That is theset of mold faces comprises a cylindrical interior face 12 c, a lowerend face 12 b, a lower side face 12 a, an upper side face 12 c, acylindrical end face 12 f and a top end face 12 e. These set of facesform the boundary surfaces for defining the battery part which is diecast with the present invention. The surfaces defined by the set offaces have a volume designated by V₁. It is within the volume V₁ thatthe finished battery part would solidify into a battery part withminimum cracks and tears.

[0035] In order to illustrate the volume of the battery part mold cavityV₂ in the unreduced state dashed lines have been included to illustratethe position of the gate 17 for supplying molten lead to the cavity aswell as the vent 18 for discharging air and excess lead. The annularsurface identified as 12 e′ identifies the position of the mold when themold is in an open condition and the annular surface 12 e identified theboundary of the mold cavity 16 in closed condition but not yet in apressurized condition. V identifies the contracted volume₁. Thus the endannular face 12 e can be brought downward to decrease the first volumeV₂of the battery part cavity by forcing the annular mold face 12 etoward the battery part cavity 16 while the molten lead in the batterypart cavity is at least partially in an unsolidified state. Bymaintaining the battery part cavity 16 in a decreased volume during asolidification of a battery part one inhibits the formation of cracksand tears in a die cast battery part.

[0036] Thus the method of die casting a battery part comprises injectinga lead containing metal in a molten state into an open battery partcavity 16 which is partially defined by a mold 11 and 12. By closing thebattery part cavity 16 by bringing a member 14 with a finished mold face12 e toward the open battery part cavity 16 partially defined by themold 11 and 12 one shuts of the passage ways 17 and 18 to create aclosed battery part cavity 16 to thereby prevent further lead containingmetal in a molten state from entering or leaving the closed battery partcavity 16. By increasing the pressure of the lead in the closed batterypart cavity 16 one can force lead that is in a molten state in thebattery part cavity into any solidification voids in lead in the closedbattery part cavity 16 to thereby inhibit the formation tears and cracksin the batter part.

[0037] The present method can include the step of maintaining the moldfaces at a temperature below the solidification temperature of themolten lead to cause peripheral surface solidification. By allowingperipheral surface solidification to occur before the volume contractionoccurs one can force the molten lead into voids and cracks in theperipheral surface solidification thereby inhibiting the formation ofsolidification voids in the die cast part.

[0038] Thus with the present process one can form an unfinished die castbattery part with the die cast battery part having a set of boundedfaces with each of said set of bounded faces adjoining each other todefining a closed surface for the battery part. Each of faces 12 a, 12b, 12 c, 12 f and 12 e are characterized by having a continuous boundedsurface free of surface imperfections so that a battery part formedwithin the cavity is also free of surface imperfection when the die castbattery part is removed from a die cast mold.

[0039]FIG. 5, FIG. 6 and FIG. 7 illustrate the various conditions of thecavity during the process of solidification.

[0040]FIG. 5 shows the mold in the open condition with the set of moldfaces 12 a, 12 b, 12 c 12 d and 12 f forming the lower battery part moldcavity. This state is referred to as an open mold cavity since moltenlead can enter the mold cavity through the open annular top of moldcavity 16. In this condition the mold part cavity 16 can be filled withmolten metal.

[0041]FIG. 6 shows the mold in the closed condition with the set of moldfaces 12 a, 12 b, 12 c 12 d and 12 f forming the lower battery part moldcavity and annular face 12 e forming the top face of mold cavity 16.This state is referred to as a closed mold cavity since molten leadcannot enter or leave the mold cavity 16. In this condition the moldpart cavity 16 forms a bounded or confined region for the molten metal.Note in this condition the downward movement of piston 14 has sealed offboth the inlet and outlet to the mold cavity 16. Extending laterallyoutward is a cavity closing line S_(L) that identifies the point whereinthe sidewalls of piston 14 close off both the inlet and outlet for metalto the cavity 16.

[0042]FIG. 7 shows the next phase wherein piston 14 has been extendedbeyond the cavity closing line S_(L) a distance x. Note, the entire face12 e has been moved toward the mold cavity 16 to decrease the volume ofthe mold cavity 16. This is the contracted condition wherein thepressure of the molten lead has been increased sufficiently so that itinhibits the formation of tears and cracks in the solidified metal. FIG.7 illustrates that the entire face 12 e moves downward along sidewall 12f to not only reduce the volume of cavity 16 but to reduce theperipheral surface area of the faces forming the cavity 16. In addition,since the entire face 12 e moves toward the cavity 16 to contract thevolume of the cavity the solidifying battery part surfaces are notdisturbed. This results in a die cast product that, when removed fromthe mold, has a finished surface condition, thus eliminating the needfor an extra step of finishing the product.

I claim:
 1. An apparatus for die cast battery part when the molten leadis in either the liquid, solid or mush state to form a finished batterypart: a mold having a set of faces for defining a portion of an outersurface of a battery part cavity; a pin having a face thereon, said pinextending though the battery part cavity to form an inner face of abattery part cavity; an inlet for delivering lead in a molten state intothe battery part cavity; a heater for maintaining the lead in a moltenstate when the lead in a molten state is not being delivered into thebattery part cavity; a retractable piston, said retractable pistonhaving a battery part face thereon for forming the battery part cavityinto a closed volume, said battery part face extending in a side-to-sidecondition to adjoin the set of faces in the battery part cavity, saidretractable piston positionable in a first condition to allow the leadin a molten state to flow into the battery part cavity, said retractablepiston driveable toward the battery part cavity to close the volume ofthe battery part cavity to thereby shut off the flow of the lead in amolten state into the battery part cavity and to decrease the closedvolume of the battery part cavity by bringing the battery part facetoward the battery part cavity to shrink the volume of the battery partcavity without disrupting a faces on a solidifying battery partsolidifying therein to produce the battery part with an exteriorfinished surface.
 2. The apparatus of claim 1 wherein the retractablepiston has a cavity for sliding along a pin and the pressure of the leadwithin the battery part cavity is increased sufficiently to thereby forma battery part whereupon solidification is substantially free of tearsand cracks.
 3. The apparatus of claim 1 wherein the battery part facecomprises an annular face.
 4. The apparatus of claim 3 wherein theentire battery part face extends along a single plane.
 5. The apparatusof claim 1 wherein the lead in a molten state is a lead alloy.
 6. Theapparatus of claim 1 the heater extends around the inlet to maintain thelead in the inlet in a molten state when the extendible piston is in anextended condition.
 7. The method of die casting a finished battery partwhile inhibiting the formation of cracks and tears comprising the stepsof: directing a first charge of lead in a molten state into a batterypart cavity having at least one open face; extending a retractablepiston having a battery part face into the charge of molten lead in thebattery part cavity to shut off the supply of molten lead to the batterypart cavity; and continuing to extend the piston to form a closedbattery part cavity and to reduce the volume of lead in the battery partcavity to a sufficient volume so that upon solidification of the lead inthe battery part cavity it inhibits the formation of cracks and tears inthe battery part.
 8. The method of claim 7 wherein the lead in thebattery part cavity is in either a liquid, mush or solid state.
 9. Themethod of claim 8 wherein the molten lead solidifies along the surfacefaces of the battery part cavity with at least one of the battery partfaces is forced inward to reduce the volume of the battery part cavity.10. The method of claim 9 including the step of heating the first moldpart with a heater to maintain the mold in a runner in a molten state.11. The method of claim 7 wherein a portion of the lead in a runner isback flowed therein to bring the molten lead in the battery part cavityto an intensification condition.
 12. The method of die casting afinished battery part comprising the steps of: injecting a molten leadcontaining metal into a battery part cavity having a first volumedefined by a set of mold faces; and decreasing the first volume of thebattery part cavity by forcing at least one of the mold faces toward thebattery part cavity to decrease the peripheral surface area while themolten lead in the battery part cavity is at least partially in anunsolidified state; and maintaining the decreased volume during asolidification of a battery part in the battery part cavity to therebyinhibit the formation of cracks and tears in a die cast battery part.13. The method of claim 12 wherein the battery part cavity is formedwith a cylindrical interior surface and an annular end face.
 14. Themethod of die casting a finished battery part while minimize cracks andvoids in the battery part comprising the steps: forming a mold with themold defining a plurality of faces of a first portion of a battery partmold cavity; forming a gate passage fluidly connected to the firstportion of the battery part mold cavity; forming a moveable member, themoveable member having a portion defining a further face of the batterypart mold cavity with the plurality of faces and the further facedefined a surface bounded mold cavity when the moveable member is in aclosed condition; pouring a lead containing metal in a fluid state intothe gate of the mold when the mold cavity is in an open condition;allowing the lead containing metal to fill the first portion of thebattery part mold cavity; and driving the moveable member toward thefirst portion the battery mold part to close off the gate passageway;continuing to drive the movable member toward the first portion of thebattery mold part until the further face forms the surface bounded moldcavity and the internal pressure of the lead in the mold increasessufficiently to force lead into any solidification voids formed in thebatter part; and allowing the battery part to solidify under pressure;removing the mold from the battery part to produce a finished. batterypart.
 15. The method of forming a finished battery part comprising thesteps of: pouring a lead containing metal in a liquid state into an openbattery cavity defined by a first set of faces in a battery part mold;allowing the lead containing metal to begin solidification around thefirst set of faces in the battery part mold; driving a member having aportion defining a completion face toward the open battery cavity untilthe completion face on the first set of faces coact to form a closedperipheral surface; and maintaining a pressure on the batter part duringsolidification of the metal in a liquid state to force molten lead intoany solidification voids formed during solidification of the molten leadin the battery part cavity.
 17. A finished die cast battery partcomprising; a lead containing die cast battery part, said leadcontaining die cast battery part having a set of bounded faces with eachof said set of bounded faces adjoining each other to define a closedsurface on said battery part, each of said faces formed bysolidification in a mold with each of said bounded faces characterizedby being free of surface imperfections when the die cast battery part isremoved from a die cast mold.
 18. The unfinished die cast battery partof claim 17 wherein the die cast battery part interior is substantiallyfree of cracks and voids.
 19. The unfinished die cast battery part ofclaim 17 wherein the die cast battery part comprises a battery terminal.20. The method of die casting a battery part comprising: injecting alead containing metal in a molten state into an open battery part cavitypartially defined by a mold; closing the battery part cavity by bringinga member with a finished mold face toward the open battery part cavitypartially defined by the mold to create a closed battery part cavity tothereby prevent further lead containing metal in a molten state fromentering or leaving the closed battery part cavity; and increasing thepressure of the lead in the closed battery part cavity to force leadthat is in a molten state into any solidification voids in lead in theclosed battery part cavity to thereby inhibit the formation tears andcracks in the batter part.
 21. The method of claim 20 including the stepof maintaining an internal pressure in a solidified part sufficient soas to force lead in an unsolidified state into voids formed proximatesolidifying lead.
 22. The method of die casting a finished battery partcomprising the steps of: injecting a molten lead containing metal intoan open battery part cavity defined by a set of mold faces; closing thebattery part cavity with a face of a moveable member to create a closedbattery part cavity with a peripheral surface area; decreasing a firstvolume of the battery part cavity by decreasing the peripheral surfacearea; and maintaining the decreased volume during a solidification of abattery part in the battery part cavity to thereby inhibit the formationof cracks and tears in a die cast battery part.
 23. The method of claim22 including the step of maintaining the mold faces at a temperaturebelow the solidification temperature of the molten lead to causeperipheral surface solidification.
 24. The method of claim 23 whereinthe volume contraction occurs after the peripheral solidification tothereby force the molten lead into voids and cracks in the peripheralsurface solidification.
 25. The method of claim 22 including the step ofmaintaining the molten lead contain metal in a liquid state in a runner.26. The method of claim 22 including the step of heating a runner toprevent solidification of the metal in the runner as the volume of thebattery part cavity is decreased.